It is widely known that a coke with high strength is desirable for use as a raw material in the production of pig iron in a blast furnace. A coke with low strength would disintegrate in a blast furnace and thus decrease the gas permeability of the blast furnace, which leads to unstable production of pig iron.
In the production of metallurgical coke by the carbonization of coal in a horizontal chamber coke oven, the strength of the resulting coke depends on the conditions such as the method for selecting coals, the method for preparation, the carbonization conditions, the quenching conditions, and the post-treatment conditions. Among these conditions, conditions related to the equipment and operation are difficult to change drastically because of equipment constraints; therefore, the selection of coals is considered the most important factor in controlling the coke properties.
Various methods are known for blending coals to produce a coke with the desired strength, including the method discussed in Non Patent Literature 1. All of these methods involve predicting the strength of the resulting coke based on the properties of the coals to be blended and determining a blend of coals predicted to provide high strength.
It is known, however, that the conventional methods for blend determination often provide inaccurate estimation of coke strength. One example is the effect known as “coal compatibility”. For example, as disclosed in Patent Literature 1, it is known that additivity is not necessarily present between the strength of a coke produced from a coal blend and the strength of a coke produced from each coal to be blended. Although various studies have been made to identify the cause of the “compatibility” effect, no technique has been available that allows reliable “compatibility” prediction to determine a combination of coals with good “compatibility”.